MANUFACTURE OF HIGH TENSION STRUCTURAL STEEL OF 50KG*MM2 CLASS OF EXCELLENT WELDABILITY

摘要

PURPOSE:To manufacture the high tension structural steel excellent in the strength, toughness, and perfectly free from the weld cracks, without lowering the rolling efficiency, by cooling under a specified cooling condition the hot rolled steel sheet whose contents of C, Si, Mn, Al, and the carbon equivalent are specified. CONSTITUTION:The steel, containing 0.03-0.09% C, 0.05-0.40% Si, 0.5-1.80% Mn, Al 0.10% or less, and the balance of Fe together with inevitable impurities, besides, whose carbon equivalent Ceq to be represented by the formula is 0.32% or less, is ordinarily hot rolled, being followed by quenching from about 770 deg.C or more down to 500 deg.C or less, at mean colling velocity above 30 deg.C/sec over the range 770-550 deg.C; hereby, the high tension structural steel of 50Kg/mm2 class, excellent in toughness and weldability is manufactured.